1. Technical Field
The present invention relates to a developing device for use in an image forming apparatus using an eletrophotographic process such as a copier, a laser beam printer, a facsimile using plain paper, and more particularly to a developing device of the type having a developing chamber and a toner supply chamber in a unitary structure in which an elastic member is installed in adjacent to an agitating member for stirring toner particles contained in the toner supply chamber, conveying the toner particles to the developing chamber for forming a toner image, and preventing the toner particles from condensation in the toner supply chamber.
2. Background Art
In an image forming apparatus using an eletrophotographic process such as a copier, a laser beam printer, a facsimile using plain paper, a developing device is customarily used for developing an electrostatic image formed on an image carrier such as a photosensitive drum. Conventional developing device typically comes in two types: a mono-component developer such as disclosed in U.S. Pat. No. 5,016,560 for Device For Image Toner Distribution On A Developing Device issued to Asada et al., U.S. Pat. No. 5,128,722 for Developing Device Excellent In Toner Transportability issued to Natsuhara et at., and U.S. Pat. No. 5,13833,385 for Developing Device With Electrically Floating Developing Roller issued to Toyoshi et at., and a two-component developer such as disclosed in U.S. Pat. No. 4,860,063 for Method Of Controlling Developer Toner Density Of Developing Device issued to Okamoto, U.S. Pat. No. 5,034,773 for Developing Unit With A Member For Agitating The Toners In A Developer issued to Nimura et at., U.S. Pat. No. 5,095,850 for Developing Device issued to Komuro, and U.S. Pat. No. 5,177,539 for Developing Device issued to Tsuji, and U.S. Pat. No. 5,289,243 for Installation And Removal Structure Of A Developing Unit And A Toner Cartridge In An Image Forming Apparatus issued to Sakamoto.
Generally, two-component developers of a unitary structure include non-magnetic toner particles contributing to developing and magnetic carrier particles for properly charging the toner particles. Usually, in such a developing unit, the developer is carried on the outer circumferential surface of a developing roller disposed facing a photosensitive drum, and the toner particles contained in the developer are made to adhere to an electrostatic latent image on the photosensitive drum as the developing roller revolves in order to develop the latent image into a toner image. Since the toner in the developer in the developing unit is gradually consumed as it is used for developing electrostatic latent images, new toner is supplied as needed to the developing unit from a toner supply chamber. In the developing unit, an agitation roller and a mixing roller are disposed beneath the toner supply chamber in order to adequately agitate and mix the supplied toner into the developer accommodated in the developing chamber. A doctor blade is also installed in the developing chamber to regulate the amount of developer carried on the rotating surface of the developing roller.
Mono-component developers of a unitary structure are generally simpler and can be made smaller in size and lower in cost, as compared with the two-component developers. Mono-component developers are typically classified into magnetic and non-magnetic developers. In principle however, a developing roller is set between a photosensitive drum and a toner supply chamber. A toner supply roller which supplies toner to the developing roller and a coating blade are pressed against the developing roller. Rotation of the toner supply roller causes toner particles to be transferred to the developing roller so as to form a thin toner layer on the developing roller. As the developing roller is rotated, a single-component toner adheres to the surface of the developing roller by triboelectronic charges between a coating blade and toner particles, and between the developing roller and the toner particles. Then, the toner particles, supported on the developing roller are caused to adhere electrostatically on a photosensitive drum to form an electrostatic latent image.
In both types of developers, it is important to effectively supply toner contained a toner supply chamber into a developing chamber for developing a toner image. Conventional developing device typically provides an agitation member in a toner supply chamber to agitate the toner particles and feed the toner particles into a toner supply roller located on the side of the photosensitive drum. The agitation member provided in the toner supply chamber comes in many sizes and shapes; but, by at large, it has been our observation that the typical configuration of the agitation member fails to enhance the fluidity of the toner contained in the toner supply chamber. Since the interior of the toner supply chamber is always greater than a turning radius of the agitation member, many toner particles remain stagnated, condensed and unused in the area therebetween. This results in a deterioration of fluidity of the toner, condensation of the toner particles, and consequently a waste of otherwise usable toner particles. Moreover, since most toner supply chambers for use in conventional developers are installed vertically using gravity as a means to gravitate the toner particles to the developing chambers, spatial arrangement of the conventional developers is severely restricted, and as a result, the developers may not be constructed in small sizes.